Method of controlling a pulp refiner by measuring freeness and removing the latency from the pulp

Abstract

Immediate and accurate control of a pulp refiner is provided so as to control the degree of refining in the production of mechanical pulp, such as RMP, TMP, and CTMP. The mechanical pulp discharged from a refiner is fluidized by a fluidizing centrifugal pump, the fluidizing action instantaneously removing the pulp latent properties. A sample of the latency-removed pulp is then subjected to a pulp freeness measurement, and that freeness measurement is supplied to a computer. The computer utilizes the freeness measurement, as well as other measurements such as pulp consistency and flow rate measurements, and dilution flow measurements, and in response to the inputs control refiner parameters to ensure that the freeness of the mechanical pulp being produced is within the desired range. The refiner parameters controlled can be the hydraulic plate loading (refining pressure), and/or the tonnage of fiber supplied to the refiner.

What is claimed is: 
     
       1. A method of controlling a refiner which refines comminuted cellulosic fibrous material to produce mechanical pulp having latent properties, comprising the steps of: (a) fluidizing mechanical pulp having a consistency of about 8-25 percent shortly after discharge from the refiner so as to effect substantially complete removal of the latency thereof, by, and during, centrifugal pumping of the pulp while it has a consistency of about 8-25 percent in a generally non-return path;   (b) continuously measuring freeness of a sample of the latency-removed pulp, and wherein the only portion of the pulp not passing in the non-return path is the sample, the sample being recirculated after freeness measurement; and   (c) in response to the measurement obtained in step (b), automatically controlling refiner parameters to ensure the mechanical pulp produced has desired freeness properties.   
     
     
       2. A method as recited in claim 1 wherein step (c) is practiced by controlling the specific loading of the refiner. 
     
     
       3. A method as recited in claim 2 wherein the specific loading controlling is provided by controlling the tonnage of cellulosic material supplied to the refiner, and/or by controlling the refining pressure. 
     
     
       4. A method as recited in claim 3 wherein step (c) is further practiced by measuring the consistency and the flow of the latency-removed mechanical pulp, and feeding the consistency and flow measurements, as well as the freeness measurement from step (b), to a computer which operatively controls the refiner parameters. 
     
     
       5. A method as recited in claim 4 comprising the further step of diluting the mechanical pulp prior to practice of step (a) so that it has a consistency of between about 8-25% when it is fluidized. 
     
     
       6. A method as recited in claim 5 comprising the further step of diluting the mechanical pulp sample utilized in the practice of step (b) so that it has a lower consistency than the pulp during fluidization thereof. 
     
     
       7. A method as recited in claim 1 wherein step (c) is further practiced by measuring the consistency and the flow of the latency-removed mechanical pulp, and feeding the consistency and flow measurements, as well as the freeness measurement from step (b), to a computer which operatively controls the refiner parameters. 
     
     
       8. A method as recited in claim 1 comprising the further step of diluting the mechanical pulp prior to practice of step (a) so that it has a consistency of between about 8-25% when it is fluidized. 
     
     
       9. A method as recited in claim 8 comprising the further step of diluting the mechanical pulp sample utilized in the practice of step (b) so that it has a lower consistency than the pulp during fluidization thereof.